Effects of Buprenorphine on Embryonic Implantation in Mice: Considerations for its use as a Post-operative analgesic following embryo transfer. Embryo transfer is a necessary procedure used in developing transgenic animals. The technique involves opening the abdominal cavity, retracting the proximal end of the uterine horn, creating a small incision in the uterine horn and injecting blastocysts into the uterine lumen. Another commonly performed procedure involves injections of early stage embryo's into the oviduct. These procedures are considered major survival surgeries in which analgesics should be considered. There is a concern among researchers that the use of buprenorphine (a partial Mu receptor agonist) as a postoperative analgesic will have adverse effects on embryonic survival and implantation. The concern is based on a disclaimer by the drug company included in the package insert. There have been no studies published that indicate adverse effects of buprenorphine on early embryonic survival, implantation, or other indices of reproductive capacity at therapeutic doses. Furthermore, the studies done by the drug company were only suggestive of such effects, but the data was inconclusive.